OBJECTIVES: The overall objective of this project is to provide detailed physiological and biochemical information on selected aspects of the cardiac uptake, storage and utilization of lipids, which are considered to be the primary source of energy for the mechanical function of the heart. The experimental models which are being employed include (a) isolated rat heart in a closed recirculating perfusion system; (b) adult heart cells (a preparation initially developed during the course of these studies); (c) specific subcellular fractions; and where feasible, (d) in vivo studies. GOALS FOR THE CURRENT YEAR: (a) To elucidate the role of lipoprotein lipase (LPL) in the uptake of triglycerides of very low density lipoproteins (VLDL) by the isolated cardiac myocyte. (b) To localize the enzyme (LPL) in or on the myocytes using immunochemical techniques. (c) To determine the apoprotein and lipid compositions of the "remnant" particle(s) obtained following triglyceride removal from VLDL during recirculating heart perfusion. (d) To determine the role of HDL in removal of specific lipids and apoproteins from "remnant" particles. (e) To elucidate the mechanisms of altered VLDL metabolism by hearts from streptazotozin-induced diabetic rats.